1. Field of the Invention
The present invention relates to matched filters and correlators and, more particularly, to a novel fast correlator transform (“FCT”) and to methods and systems for implementing same.
2. Related Art
Matched Filter Theory was introduced by D. O. North in 1943. Others such as Van Vleck, Middleton, Weiner, and Turin, have added to the body of knowledge and application, ranging from RADAR to SONAR and communications. Although the basic theory was originally applied to continuous time systems and linear networks, the theory has been augmented to absorb discrete sampled filters and correlator operations. Indeed Paul Green pointed out in the June 1960 IRE Transactions on Information Theory, Matched Filter Issue:
“Correlation detection was studied at first as a separate subject, but the equivalence of the two operations (meaning matched filters and correlators) was soon appreciated.”
IRE Transactions on Information Theory, New York, N.Y.: Professional Group on Information, Institute of Radio Engineers, June, 1960, incorporated herein by reference in its entirety.
More recently Van Whalen and Blahut as well as others have provided proofs of mathematical equivalence of correlation or matched filtering based on a change of variables formulation.
With the surge of DSP and proliferation of VLSI CMOS circuits as well as the universal push for software radios, many discrete matched filter realizations have evolved. The most notable digital implementation is the Transversal or Finite Impulse Response Filter which may realize the time flipped impulse response of the waveform to be processed or utilized as a correlator, both which produce the equivalent result at the optimum observation instant.
A particular concern arises when multiple filtering operations are required, concurrently, as is the case for parallel correlators. The complexity, clock speeds and signal flow control typically increase cost, size, and power.
What are needed are improved methods and systems for performing matched filtering and/or correlating functions, including concurrent and/or parallel correlations.